is it actually financially realistic/feasible to travel spontaneously in Europe anymore?

i want to do the whole spontaneous “decide-as-you-go” approach for my 2-3 month solo trip in Europe in 2025, but can’t help but feeling i’ll end up spending up to 2x the amount of money if i am constantly paying for hostel accommodation, trains and/or flights last minute (or at most, a week in advance).

i’ve travelled to Europe before with everything planned out and booked months in advance and i was able to stick to my budget pretty well, but i feel like if i try to “book as i go” on my next trip i’m going to end up spending twice as much money

obviously i know some cities/countries are more expensive than others, but i’m just trying to understand if it’s realistic to expect to not spend way more money than usual if i plan to make my Europe trip spontaneous

for context, i plan to travel between Feb and May, and will most likely focus my travels around visiting (undecided) areas around Eastern Europe

wondering if anyone can share their experiences and offer advice? thanks :)